Further insight into the stereoselective interaction between warfarin and cimetidine in man.

The urinary profile of R- and S-warfarin, following administration of a single (25 mg) oral dose of racemic warfarin, alone or on day 4 of a 9-day chronic administration of cimetidine (800 mg once daily), was investigated in eight healthy male volunteers. Based on estimated apparent formation clearance values, cimetidine inhibited significantly only the formation of R-6-hydroxywarfarin and R-7-hydroxywarfarin.